Vegetarian robots: Munching machines

A ROBOT with dietary requirements might appear to be a bit far fetched, but a team of American researchers is developing a machine to power a vehicle that will fend for itself by gathering material like wood, leaves and grass to be used as a biofuel to run its steam-driven engine. Who might want such a device? The American military.

The Energetically Autonomous Tactical Robot is known, of course, by its acronym: EATR. It is the brainchild of Robotic Technology of Washington, DC. So far it is only a concept, but a working prototype is in the works. The research, in part funded by America’s Defence Advanced Research Projects Agency, is seen as a way to help soldiers reduce their dependence on fuel supplies. The robot could, for instance, forage for biofuel while a unit on a long-endurance mission rested. It could then be used to recharge their electrical devices, carry some of their equipment or transport the soldiers as well.

The EATR uses a robotic arm to gather and prepare vegetation, which it feeds through a shredder into a centrifugal combustion chamber, where it is ignited and then heats a series of coils. The coils contain deionised water (to stop them from furring up like a kettle). As the water inside the coils is superheated the steam is piped to a radial steam engine, which consists of six pistons. The steam rotates the pistons, driving a generator which produces electricity. This is stored in batteries that power the electric motors which drive the EATR along.

The steam engine is designed to be a “closed-loop” system, in which water escaping from the cylinders through the exhaust ports is captured and cooled in a condensing unit. This turns the steam back into water, which is then returned to the combustion chamber. As well as using biomass, EATR’s engine could also run on petrol, diesel, kerosene, cooking oil or anything similar than could be scavenged. The ability to consume a wide range of fuels would be important if the vehicle travels through areas like deserts, where vegetation may not be available and alternative fuel has to be provided.